JPH0822929B2 - Method for forming thin film of perfluoropolymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a perfluoropolymer having a fluorine-containing ring structure in its main chain under a thin film.

[Prior Art] Conventionally, as fluoropolymers, polytetrafluoroethylene (PTFE), perfluoroalkoxy vinyl ether / tetrafluoroethylene copolymer (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), Polychlorotrifluoroethylene (PCTF
E) and the like are known, but since these fluoropolymers are generally insoluble in a solvent, thin film formation is performed by a melt molding method or a combination method of melt molding and cutting.

[Problems to be Solved by the Invention] However, in the conventional fluoropolymer,
When thinning these, especially when trying to obtain a thin film of 50 μ or less, defects such as pinholes occur, or large molding pressure and stretching force are required, which is disadvantageous for industrial implementation Met. In particular, with respect to perfluoropolymer, the above-mentioned difficulties are remarkable, and it has been difficult to smoothly and advantageously obtain a defect-free thin film having a thickness of 50 μm or less.

An object of the present invention is to provide a perfluoropolymer thin film with a thickness of 50 μm or less and a defect-free thin film without impairing its properties, and to provide a method for thinning a perfluoropolymer which can be carried out industrially smoothly and advantageously. To do.

[Means for Solving the Problems] As a result of various researches and studies, the present inventor has adopted a perfluoropolymer having a ring structure in the main chain, and thus, even in the case of a perfluoropolymer, It was found that a thin film can be easily formed, and a thin film having a size of 50 μm or less can be smoothly and advantageously manufactured. Furthermore, by dissolving the specific perfluoropolymer in a solvent of the perfluoro compound and using the solution, there is no defect even in an ultra-thin film of 20 μ or less, for example about 0.02 to 5 μ, which has not been obtained until now. It has been found that it can be a membrane.

Thus, the present invention has been completed based on the above findings, and a novel perfluoropolymer thin film characterized in that the perfluoropolymer having a ring structure in the main chain is thinned to a thickness of 50 μm or less. Is provided to.

In the present invention, examples of the perfluoropolymer having a ring structure in the main chain include those represented by the general formula: And those having a ring structure such as Of these,
Polymers having the following ring structures are typical. However, the content of the present invention is not limited to these.

The methods for producing these polymers are as follows.
However, it is not limited to these manufacturing methods.

1. By cyclopolymerization 2. Using cyclic monomers (such as USP 3978030) The polymerization reaction is not particularly limited as long as it proceeds radically, and examples thereof include polymerization by an organic or inorganic radical initiator, light, ionizing radiation or heat. The method of polymerization is also not particularly limited, so-called bulk polymerization in which the monomer is directly subjected to polymerization, solution polymerization performed in an organic solvent in which the monomer is dissolved,
Examples thereof include suspension polymerization carried out in an aqueous medium in the presence or absence of a suitable organic solvent, and emulsion polymerization carried out by adding an emulsifier to the aqueous medium.

Further, there is no problem in using the copolymerization component to the extent that the essence of these components is not impaired. Other monomers to be copolymerized are not particularly limited as long as they are radically polymerizable monomers, and fluorine-containing compounds can be widely exemplified. As a matter of course, one of these other monomers may be used alone for radical copolymerization with a monomer capable of introducing the specific ring structure into the main chain as described above, or two or more of them may be used in combination. You may make it carry out the said copolymerization reaction. In the present invention, it is usually desirable to select a fluorine-containing monomer such as fluoroolefin or fluorovinyl ether as the other monomer. For example, tetrafluoroethylene and perfluorovinyl ether are suitable specific examples.

The composition of the copolymer preferably has a cyclic structure of 20% or more, more preferably 40% or more, in order to take advantage of the solubility, film-forming property, and properties of the fluoropolymer. Such a polymer is soluble in a solvent, and the solvent used is not limited as long as it dissolves the above polymer, but perfluorobenzene, "Aflude" (trade name: fluorine-based solvent manufactured by Asahi Glass Co., Ltd. ), "Fluorinert" (trade name: liquid containing perfluoro (2-butyltetrahydrofuran) manufactured by 3M)
Solvents of perfluoro compounds such as As a matter of course, two or more appropriate types can be used in combination as a solvent. Especially in the case of a mixed solvent, a hydrocarbon type,
Chlorinated hydrocarbons, fluorochlorinated hydrocarbons, alcohols, and other organic solvents can be used together. Solution concentration is 0.01 wt% to 50 wt%
And preferably 0.1 wt% to 20 wt%.

The thin film formation method uses the above solution, a roll coater method,
There is no particular limitation as long as it is a method of forming a film from a solution such as a casting method, a dipping method, a spin coating method, a water casting method, and a Langmuir-Projet method.

The obtained thin film can be used as it is adhered on the base material or separated from the base material, and when used while being adhered on the base material, any shape and any material is applied to the base material. . For example, magnetic disk substrates, optical fibers, electric wires, lens materials, separation membrane supports, hollow fibers, various tapes such as magnetic tapes, optical glass materials, electrodes, medical materials such as blood bags, various building materials, stainless steel, glass, aluminum, metals, Furthermore, currently used fluororesin paints, PFA, ETFE, PTFE, PCTFE, PVdF, FE
A substrate coated with a fluorine-containing resin such as P may also be exemplified.

The thin film has no defects such as pinholes, is transparent and has a low refractive index, and is excellent in heat resistance and chemical resistance, and thus can be used for various coating materials, electronic members, optical members, separation films, and the like.

[Function] In the present invention, the reason why the perfluoropolymer having a ring structure in the main chain is easy to form a thin film is that the polymer is soluble in the solvent of the perfluoro compound and various thin film forming methods such as dipping and spin coating are used. This is because it can be used. Further, the reason why this polymer is soluble in a special solvent is not clear, but it is considered that the solvent and the polymer have similar ring structures and the crystallinity of this polymer is low.

Examples Synthesis Example 1 30 g of perfluoroallyl vinyl ether, 30 g of trichlorotrifluoroethane and a polymerization initiator 10mg of was placed in a 50cc pressure resistant ampoule. After freeze-deaeration was repeated twice, polymerization was carried out at 20 ° C. for 16 hours. The pressure during polymerization was below atmospheric pressure. As a result of the polymerization, 16 g of a polymer was obtained.

When the infrared absorption spectrum of this polymer was measured, there was no absorption near 1790 cm ⁻¹ due to the double bond in the monomer. When this polymer was dissolved in perfluorobenzene and the ¹⁹ F NMR spectrum was measured, the spectrum showing the following repeating structure was obtained.

The intrinsic viscosity [η] of this polymer is "Fluorinert" FC
It was 0.530 at 30 ° C. in −75 (trade name: liquid containing 3M company perfluoro (2-butyltetrahydrofuran) as a main component, hereinafter abbreviated as FC-75). The glass transition temperature of the polymer is 69 ° C., and it is a tough and transparent glassy polymer at room temperature. The 10% thermal decomposition temperature is 462 ° C, and the polymer is colorless and transparent and has a low refractive index of 1.34.
The light transmittance was as high as 95%.

Synthesis Example 2 30 g of perfluoroallyl vinyl ether, 30 g of trichlorotrifluoroethane and a polymerization initiator 10mg of was placed in a 50cc pressure resistant ampoule. After freeze-deaeration was repeated twice, polymerization was carried out at 30 ° C. for 16 hours. The pressure during polymerization was below atmospheric pressure. As a result of the polymerization, 19 g of a polymer was obtained.

The structure of the polymer was confirmed by the same method as in Synthesis Example 1.
The intrinsic viscosity [η] of this polymer is 0.32 at 30 ℃ in FC-75 solution.
Met.

Synthesis Example 3 10 g of perfluoroallyl vinyl ether, 1 g of tetrafluoroethylene, and trichlorotrifluoroethane
30g and polymerization initiator 5mg of was placed in a 100cc pressure resistant ampoule. After freeze-deaeration was repeated twice, polymerization was carried out at 30 ° C. for 6 hours. As a result of the polymerization, 4 g of a polymer was obtained.

^From the measurement of ¹⁹ F NMR spectrum, this copolymer It was found that the structure and composition were like.

Example 1 5 g of the polymer obtained in Synthesis Example 1 was converted into 95 g of "Aflude".
It was dissolved in E-10 (trade name: perfluoro (2-butyltetrahydrofuran) manufactured by Asahi Glass Co., Ltd.).

This solution was cast on a stainless steel substrate and placed under a nitrogen stream.
When the solvent was removed by treatment at 16 ° C. for 16 hours and 110 ° C. for 5 hours under reduced pressure, a 20 μm wet film was formed. When this thin film was peeled from the substrate, it was a transparent film without defects such as pinholes. The tensile strength of this film was 300 kg / cm ² , and the tensile elongation was 160%.

Example 2 The solution used in Example 1 was cast on a glass plate and treated under a nitrogen stream at 40 ° C. for 16 hours and under reduced pressure at 110 ° C. for 5 hours to remove the solvent, and a 3 μm thin film was formed.

Example 3 A plastic lens (diethylene glycol bisallyl carbonate type) was attached to the solution used in Example 1 and spin coating was performed. After spin coating at a spin speed of 1500 rpm for 5 seconds and drying at 60 ° C. for 1.5 hours in a nitrogen stream, a 1 μm thin film was coated on the lens.
This lens can be used as a low reflection processed lens.

Example 4 The solution used in Example 1 was applied to a quartz glass fiber, introduced into a heating and curing furnace maintained at 400 ° C., and allowed to pass for 2 seconds to give 5 on the quartz glass fiber.
An optical transmission fiber having a μ coating was obtained.

Example 5 1 g of the polymer of Synthesis Example 2 was dissolved in 99 g of "Aflude" E-16 (trade name: perfluorotributylamine manufactured by Asahi Glass Co., Ltd.) and spin-coated on a metal substrate. The spin speed was 5000 rpm and the rotation was for 1 minute. Then, when dried at 50 ° C., a 0.05 μ thin film was formed on the metal substrate. The absence of pinholes in this thin film was confirmed by measuring the electrical resistance of this thin film to be> 10 ¹⁵ Ωcm.

Example 6 1 g of the copolymer of Synthesis Example 3 was dissolved in 99 g of perfluorobenzene. After immersing the aluminum substrate in the above solution
When dried at 40 ° C. for 1 hour, a 1.5 μ thin film was formed on the aluminum substrate.

Comparative Example 1 5 g of the polymer of Synthesis Example 1 is 95 g of 1,1,2-trichloro-1,
It did not dissolve in 2,2-trifluoroethane but only swelled.

EFFECTS OF THE INVENTION The present invention dissolves perfluoropolymer having a ring structure in the main chain in a special solvent, and forms a thin film using this solution to industrially and smoothly produce a thin film of 50 μm or less. Since the polymer having a perfluoro ring structure in the main chain is soluble in a solvent even if it is a homopolymer, it is soluble even in a polymer or copolymer having a high fluorine content. Therefore, the obtained thin film has properties as a fluororesin, such as low refractive index, heat resistance, low moisture permeability,
High resistance, high dielectric breakdown strength, etc. are not reduced.

Further, since it has a ring structure in the main chain, it has a feature that a transparent thin film having low crystallinity can be obtained.

In the copolymer, since it is possible to select a comonomer having various useful functions, it is possible to impart more functions to the thin film.

Claims (1)

[Claims] 1. A thin film, characterized in that a thin film of the perfluoropolymer having a thickness of 50 μm or less is formed using a solution of a perfluoropolymer having a fluorinated ring structure in its main chain dissolved in a solvent of a perfluoro compound. Method.